Conventionally, a printing plate is used for relief printing, intaglio printing, and lithographic printing on an object to be printed such as a packing material, a label, and a magazine. A relief printing plate is used for the relief printing. Examples of the relief printing plate include a flexographic printing plate, which may be applied to printing on various objects to be printed because of its flexibility.
Generally, a flexographic printing plate precursor comprises a photosensitive resin layer made of a photosensitive resin composition on a support made of such as a polyester film. A flexographic printing plate is made by exposing the photosensitive resin layer of the precursor to ultraviolet light according to a predetermined image and by removing unexposed portions of the resin.
In the case of a flexographic printing plate precursor for so-called analog printing, a negative film having a preformed image is put on the photosensitive resin layer, and the layer is exposed to light through the negative film to reproduce the image. Meanwhile, in the case of a flexographic printing plate precursor for laser-ablation-mask (LAM) printing, an infrared ablation layer is preformed on the photosensitive resin layer. A predetermined negative pattern is formed by directly transferring a negative image in a form of digitized information onto the infrared ablation layer with an infrared laser beam. Then, the photosensitive resin layer is exposed to light thorough the obtained negative pattern to reproduce the negative pattern on the surface of the photosensitive resin layer.
Adhesion between the photosensitive resin layer and the infrared ablation layer is important for the flexographic printing plate precursor for LAM printing, since the infrared ablation layer is preformed on the photosensitive resin layer.
In view of the importance of the adhesion, for example, PTL1 discloses the adhesion between a photosensitive resin layer and an infrared ablation layer is increased when the infrared ablation layer contains a binder polymer that is compatible with a binder polymer contained in the photosensitive resin layer.